Part Number: TMS320F28069M
Other Parts Discussed in Thread: DRV8305
Hi,
I am using the F28069M Launchpad with BOOSTXL-DRV8305 for motor control.
My motor is a PMSM; 48V, 200W, details below from the datasheet:
Since the DRV8305 booster pack only supports up to 45V, I am using a 42V/5A power supply.
I have done the Motor parameter identification process (lab 02a), offset calculations (lab 03a), and intertia identification (lab 05c, lab 12a) and updated values in user_J1.h as per these labs.
My values are as below:
I_A_offset (1.006295741)
I_B_offset (1.005285263)
I_C_offset (1.005504012)
V_A_offset (0.8802801371)
V_B_offset (0.8761173487)
V_C_offset (0.8745301962)
Motor parameters:
USER_MOTOR_TYPE MOTOR_Type_Pm
USER_MOTOR_NUM_POLE_PAIRS (5)
USER_MOTOR_Rr (NULL)
USER_MOTOR_Rs (0.264125049)
USER_MOTOR_Ls_d (0.000289917)
USER_MOTOR_Ls_q (0.000289917)
USER_MOTOR_RATED_FLUX (0.059309903)
USER_MOTOR_MAGNETIZING_CURRENT (NULL)
USER_MOTOR_RES_EST_CURRENT (3)
USER_MOTOR_IND_EST_CURRENT (-3)
USER_MOTOR_MAX_CURRENT (7.0)
USER_MOTOR_FLUX_EST_FREQ_Hz (20)
USER_MOTOR_ENCODER_LINES (1000)
USER_MOTOR_MAX_SPEED_KRPM (3.0)
USER_SYSTEM_INERTIA (0.04)
USER_SYSTEM_FRICTION (0.345)
I have tried lab 04 (torque mode) and some of labs 12x and 13x and they all seem to work well ( just sanity check under no/small loads)
I was then using the velocity mode in lab 12b to test performance of the combo in a traction application (pulling and rolling paper on a roll) and wasn't getting enough power. Speed was set to 0.03krpm and USER_MOTOR_MAX_CURRENT was set to 7.0
I noticed that even when the motor was stalling, and while IqRef_A was showing 6.9999, the current consumption on the power supply was no more than 0.6A (at 42V). At less than 25W of power, I realized that I shouldn't expect a lot of torque from the motor. I therefore changed USER_MOTOR_MAX_CURRENT to higher values (up to 20) and started getting good torque. With a value of USER_MOTOR_MAX_CURRENT = 20, at full load on the motor, IqRef_A was going to a max of 19.999 and on the power supply, the current went to about 4A maximum.
Please excuse my lack of knowledge on the matter, but I would like to know how the IqRef_A value corresponds to the actual RMS current going through the windings at any point in time? I assume the 6.4A rated current in the datasheet is the sustained RMS current that can go through the windings without damaging my motor. But then why do I see less than 25W of power consumption on my power supply at that time? Or did I miss a lab and now my values are not scaled properly?
Kindly clarify.
Best Regards,
Saad Tiwana
